Make cake mix as directed on the package, using the eggs, water and oil.
Line muffin pans with paper liners.
Fill muffin cups 2/3 full.
Bake in 350 degree oven for 20 - 25 minutes -OR- until center is set and top springs back when toughed.
Cool on wire rack completely.
For the pudding:
In a saucepan, combine the sugar, cornstarch and salt. Slowly stir in milk until blended completely. Continue to stir over MEDIUM heat until thick and bubbly. Cook and stir 5 minutes longer over LOW heat.
Remove from the heat.
Add a small amount of hot mixture into beaten egg yolk to bring it up in temperature. Add a little more and mix again.
Spoon mixture back into the pan.
Stirring constantly bring the mixture to a gentle boil. Cook and stir another minute longer.
Remove from the heat. Slowly stir in butter and vanilla. Cook another 5 minutes.
Cool for 30 minutes, stirring occasionally.
Cover and refrigerate for 1 hour.
Place cold pudding in pastry bag and pipe pudding into cupcakes from the top. You should feel the cupcake begin to fill but you don't want it to crack. You can also use a spoon, melon baller or apple corer to scoop out a small portion of the cake and add about a tablespoon of pudding in the hole you just made.
Once filled set aside.
For the glaze you will place all the ingredients in a sauce pan and melt over low heat or in a double boiler. Stir constantly until smooth and creamy.
Dip cupcake tops in the chocolate glaze being sure to cover each well. Continue until all cupcakes have been dipped.
Refrigerate 30 minutes to an hour to set the chocolate and the pudding.